Cells generate gene or protein, and controls biogenic activities, such as controlling over metabolic product, immunity system, proliferating differentiation. Research on or analysis of the cells is thus ever progressing not only for clearing up the mechanism of biological reaction but also for advancing the medical diagnosis.
Cells preserved in a culture solution are often extracted into a test solution for analyzing the cells with a centrifugal separator or a pipette. However, this method with those devices is a time-consuming job, and the cells may brake during the centrifugal separation, so that precious cells and an expensive culture solution in great quantity are consumed more than a necessary amount of the culture.
To overcome the foregoing problem, a device produced by a Micro Electro Mechanical System (MEMS) technology is developed. Among devices produced by the MEMS technology, a device employing acoustic waves can handle the cells without contact, and includes a small sound source with a piezoelectric element which is easily controlled. Patent Document 1 discloses a cell pretreatment in which a device employing acoustic waves. The cell pretreatment extracts a mixture solution containing cells and first solution simultaneously are introduced in a flow channel having a separation function. Non-Patent Document 1 discloses cells are extracted into second solution with acoustic waves. Another citation discloses that an inlet channel for the second solution and an outlet channel for the first solution having the cell extracted are connected continuously to a flow channel having an extracting function.
FIG. 15 is a plan view of a conventional component separating device disclosed in Non-Patent Document 1 for illustrating a method of extracting solid particles with the conventional device. As shown in FIG. 15, mixture solution containing solid particles 120 and first solution 123 are put into first inlet channel 103 along direction 130. Simultaneously to this, second solution 124 is put into second inlet channel 104 along direction 131. An acoustic wave produced by acoustic-wave generator 111 is transmitted to flow channel 102, thereby generating a standing wave having node 138 existing at the center of flow channel 102.
Radiation pressure from the acoustic wave causes the standing wave to apply, to solid particles 120, a force directed toward the center of flow channel 102, so that solid particles 120 move from a flow of first solution 123 into a flow of second solution 124, i.e. particles 120 are extracted from first solution 123 into second solution 124. Then, outlet channel 105 discharges mixture solution containing second solution 124 and extracted solid-particles 120 along direction 132, and allows first solution 123 and remaining particles 120 which are not extracted into second solution 124 to flow out along direction 133.
However, although an effort is directed toward extracting solid particles 120 as many as possible by using the foregoing conventional device, the dispersion in position of particles 120 with respect to the width direction of second inlet channel 104 as well as the dispersion in size of individual particles 120 prevents particles 120 from being completely extracted into second solution 124.
Patent Document 1: JP2004-535912A
Non-Patent Document 1: Per Augustsson et al., μTAS 2006, pages 627-629